This invention relates to imrovements in and relating to an apparatus for the evaluation of yarn qualities.
As commonly known among those skilled in the art, yarn qualities comprise mainly physical properties such as strength and elongation values, chemical properties such as dyeing characteristics and morphologic tendency such as slub-formation, regardless of the kind and nature of the yarn, as of natural, synthetic or regenerated fibers.
In present advanced manufacturing process or finishing modes of these fibers, and in each of various and numerous processing steps, such as those of spinning, stretching, false-twisting, threading and sizing, it is possible to manage and control these values roughly within respective specified ranges, while it may be unavoidable that these practical values are subjected to appreciable fluctuation caused by a certain or other reason. It is, therefore, just an ideal to make the yarn quality evaluation, depending upon the degree of fluctuation of these characteristic values.
According to the conventional technique, it has been impossible to make a yarn quality evaluation on line in the yarn manufacturing or processing stage, such as its spinning, stretching, false-twisting, threading, sizing or the like step and concurrently in a combined manner of several yarn qualities, thus the realization of a multi-functional evaluation mode as above, has been a dream of the person skilled in the art.
As is commonly known, the micro-structure of the fiber may be explained briefly as follows:
The man-made fiber comprises a chain of high molecules which are arranged in a highly complicated manner within the fiber which can be said after all as representing a mixture of crystalline regions with amorphous regions.
The mechanical characteristic of the fiber can be expressed by its strength and the degree of elongation, as a representative example and for a practical purpose. Thus, the crystalline region reflects the strength of the yarn, while the amorphous region reflects the degree of elongation thereof. Therefore, yarn strength and its degree of elongation, in combination, can be deemed as the overall characteristics both kinds regions.
When the yarn is subjected to a forced vibration, the amorphous region represents the viscous nature of the yarn, while the crystalline region represents the elastic behavior thereof, thereby the visco-elastic nature of the yarn is the combination of both kinds behaviors.
On the other hand, when the fiber is dyed with a dyestuff, the amorphous region will play an important role. At the amorphous region, the dyestuff is easily diffused therein, regardless of the characteristic of the dyestuff which may have its dyeing performance based substantially upon its chemical or physical behavior. Therefore, the probability of existence of the dyestuff in the amorphous region is substantially higher than in the crystalline region, thus the former region is substantially easier to dye than the latter region.
On the other hand, the crystalline region presents a considerable difficulty in the diffusional affinity to such dyestuff as predominating its physically acting dyeing performance, and thus, this region can be dyed only with difficulty due to the lower prevailing percentage of the above kind of dyestuff. However, such dyestuff as predominating its chemically acting dyeing performance has a high chemical affinity to the crystalline region and is likely to occupy the dyeing seats prevailing in the material crystalline region of the yarn. Thus, this region is more likely to be dyed on account of higher rate of existence of the dye particles.
In the case of dyeing a yarn which is believed to have these crystalline and amorphous regions arranged substantially in a cyclic order when considered theoretically and in an idealized model, by means of a predominantly acting in physical or chemical behavior, the former regions will show a rather apparent difference in the dyed color tone, while the latter regions may show a rather minor difference in the dyed effect and demonstrate no appreciable difference in the color tone.
It has been known for several decades to lead a yarn continuously through a sensing gap formed between and defined by a pair of capacitive electrodes of a sensor unit, to scrutinize yarn mass or denier variation or fluctuation in a precise and continuous way. Those skilled in the art have believed that the electrical outputs from such sensor unit correspond exclusively to the yarn mass or denier variation or fluctuation. However, according to our profound experimentation, it is now found that the electrical output information of the capacitive sensor represents not only the mass or denier variation, but there is also additional and overlapped information which has an intimate corelationship with the visco-elastic characteristic distribution of the yarn under test. The latter characteristics are substantially influenced by the microstructure of the fibers, or more specifically, the corelationship between crystalline and amorphous structures of the yarn molecules. These micro-structural characteristics will have a substantial effect upon the macro-structural behavior of the yarn.
As for the sensor unit commonly used for the above purpose, it has generally the following order of outline dimensions, 8 mm in its length and 5 mm in its height or width. The thickness of a condenser electrode plate is generally about 0.5 mm, while the condenser gap is approximately 0.8 mm. There is provided a stationary yarn guide in close proximity to each end of the gap.
The yarn is guided through the yarn guides and led to travel through the condenser gap at a speed of 100-4,000 meters per minute.
It is observed that the yarn vibrates between the yarn guides, the vibration depending substantially upon the visco-elastic characteristics of the running yarn. With higher visco-elasticity thereof, the vibration amplitude will become larger. According to our finding, the degree of amplitude and frequency components during the yarn vibration plays a significant role in the determination of the yarn characteristic or quality.
In the case of the synthetic fiber yarn, the visco-elasticity will become larger when the yarn largely comprises amorphous regions.
In the dyeing step of the yarn, as was referred to hereinbefore, the dyestuff will be more easily diffused in and among amorphous regions or components of the yarn which characterize the viscous property of the yarn.
On the contrary, the diffusion of dyestuff in and among crystalline regions or components which characterize the elasticity of the yarn, will be rather difficult.
As the physically predominantly acting dyestuffs which are liably dispersed and adsorbed in and by the yarn material, may be raised, among others, direct dyes, disperse dyes and non-ionic dyes as representatives. On the other hand, as the chemically predominantly acting dyestuffs, may be raised among others, cationic dyes, anionic dyes and reactive dyes as representatives.
It has thus been highly difficult to anticipatingly determine the dyeing characteristics of the yarn, especially in advance of the dyeing process and even in the manufacturing step of the yarn and in the manner of the on-line mode.